Which IEEE standard defines 10GBASE-SR, 10GBASE-LR, and 10GBASE-ER?

The IEEE standard that defines 10GBASE-SR, 10GBASE-LR, and 10GBASE-ER is 802.3ae. This standard covers the specifications for 10 Gigabit Ethernet over both optical fibers and copper cables, detailing the various physical media and signaling methods used in these high-speed networking environments.

10GBASE-SR is designed for short-range transmission using multimode fiber, 10GBASE-LR is intended for long-range transmission over single-mode fiber, and 10GBASE-ER is specified for extended range transmission also using single-mode fiber. Each of these variants addresses different distance requirements and types of fiber optics to accommodate varying deployment scenarios in networks.

The other choices refer to different categories of Ethernet standards, with 802.3z primarily focusing on Gigabit Ethernet, particularly over fiber, while 802.3ab deals with 1000BASE-T, which is Gigabit Ethernet over copper. Lastly, 802.3ad specifies link aggregation, allowing for the combining of multiple Ethernet links to increase bandwidth and provide redundancy, but does not relate to 10 Gigabit Ethernet standards.